The main objective of this proposal is to understand the reactivity and coordination chemistry of new Fe/III(heme)-X-Mn/II complexes [X=bridging hydroxo (Oh)- or oxo (O2)] is functional models of manganese peroxidase (MnP). The proposed complexes contain the biologically relevant metals, Fe and Mn, that MnP requires for oxidative degradation of lignin. The proposed complexes contain the biologically relevant metals, Fe and Mn, that MnP requires for oxidative degradation of lignin. Well developed synthetic strategies and rigorous purification techniques will be carried out in order to obtain the final Fe/III(heme)-X- Mn/II product. The reactivity of the proposed compounds with peroxide should generate bridging peroxo (O2/2)-complex or possibly even a (porphyrin)Fe/IV=O intermediate similar to compound II. Biologically relevant substrates (i.e. lignin model compounds) will be introduced to the oxidized intermediates in order to test the possibility of oxidative degradation catalysis. An array of spectroscopic methods [X-ray possibility of oxidative degradation catalysis. An array of spectroscopic methods [X-ray crystallography, electroparamagnetic resonance, magnetism, paramagnetic shifted nuclear magnetic resonance, infrared, magnetic circular dichroism, electron absorption, resonance Raman] will be used to probe the geometric and electronic structure of the proposed compounds, as well as the reactive intermediates.